1. Field of the Invention
The invention relates to a method of route guidance for a person with a mobile station which is connected via a mobile telephone network to a special online service. The on-line service provides geographic information data for route guidance which a person on the move, such as a pedestrian, cyclist or the like, calls up for automatic route guidance to a desired destination. The invention additionally relates to an extension of the technical fittings for a mobile station which corrects the optical and/or acoustic output and utilization of the transmitted information data. Moreover, the invention can also be applied in any type of vehicle. The term “mobile station” describes any mobile device to which a bidirectional connection to a mobile telephone network can be established, for example a mobile telephone for a cellular radio communications network.
2. Description of the Prior Art
What is known as the global positioning system (GPS) is used to guide a vehicle in an unfamiliar region to its destination. If a GPS receiver in the vehicle receives simultaneously at least three GPS satellites the receiver can determine from the propagation delay of the signals its local position exactly to within about 20 m to 100 m. Moreover, by exploiting the Doppler effect in moving vehicles the speed, course and other navigational variables may be determined. Starting from the computed position a dead reckoning navigation unit having appropriate sensors for the motion of the vehicle determines route data on the actual direction of motion and on the distance covered.
Only once a local computer has entered the route data into an electronic map is it possible to relate one's own position to the proximate environment. The computer requires access to a database containing a substantial volume of geographic information in order to select the information for the electronic map in accordance with the desired destination. After the route has been computed this is output by acoustic or optical means.
The application of this system for the provision and detailed volume of data would not be just a problem for the pedestrians and cyclists. For the geographic information alone the computer needs a non-volatile local storage medium having high storage density such as a CD-ROM or hard disk offering a storage capacity of some hundreds of megabytes. Accordingly, the fittings are substantial and costly and due to their volume, weight and energy consumption are not well suited to a mobile station such as a mobile telephone. Over and above that, periodic updating of the information when local change occur has to be ensured.
As an alternative to this the French company Webraska Mobile Technologies SA runs a navigation service on the Internet (http://webraska.com) with a server which substantially possesses a cartographic database and a program for the computation of travel routes. The delivery of this service, in particular the computation of personal travel routes can be requested inter alia by network connection via a mobile station. The technical design of the service is set out in publication WO 98/45823. By means of appropriate textual, graphic and acoustic data entered into his/her mobile station the person transmits information about the desired destination to the server. The mobile station also has a positioning device, such as for example the aforementioned GPS receiver, and determines its own local position automatically. Alternatively, a known GSM network positioning facility can be used which calculates the current position on the basis of distances to nearby base stations in the mobile communications network. However, the data on the starting position can also be entered by the person him-/herself in the form of text and/or graphics or acoustically.
After receiving the position and destination data the navigation service computes a corresponding personal travel route and transmits this to the mobile station as route coordinates in vector form during a transmission period. That means the entire distance is transmitted as a series of coordinates for route segments so that the geometric pattern of the route is stored temporarily by means of coordinates in the mobile station and can be illustrated on a mobile station display by means of straight route segments and curved segments.
The wireless data interchange between the mobile station and the navigation service ensues in accordance with the Internet telecommunications application WAP=wireless application protocol. This is optimized for use in wireless data communications and instead of transmitting complex structured web pages transmits only text and simple graphics.
The positioning device periodically determines the current position of the mobile station and a microcomputer compares this with the local route coordinates on the transmitted travel route. In this way constant route guidance including display of the current position in a map is possible in real time and the microcomputer can immediately identify and output departures from the travel route. In order to avoid the person having to constantly observe the graphic display there is the possibility of indicating a forthcoming change of route direction by means of additional acoustic or optical outputs, for example in a mobile telephone by lower image resolution. The solution, however, imposes lower requirements on the local equipment with regard to the computer and storage capacity than other navigation systems so that route guidance for pedestrians and cyclists can be implemented. In all of the embodiments described the microcomputer is continuously making comparisons regardless of the complexity of the course of the travel route, for example at intervals of seconds, between the current local positional data and the route coordinates of the computed travel route. This is disadvantageous as was also the case for the solution described at the outset. If the mobile station moves for a relatively long time on the same road or the same route the computer and positioning device are carrying out many redundant activities which drain the battery power supply without the accuracy of the route guidance rising. This is a particularly unsatisfactory state in the case of a mobile telephone having a compact power supply.
Moreover, as a consequence of the detailed presentation of the travel route for all roads or routes not running in a straight line the route coordinates for several route segments are transmitted. This increases the cost of data transmission to the mobile station. As a result of the limited transmission bandwidth of the mobile communications network, however, only a small volume of data can be transmitted in an acceptable time so that redundancy in the data volumes should be avoided. Moreover, only a limited amount of energy is available to a user without a vehicle for determining the route.
All of the aforementioned solutions require GPS signals in each time interval simultaneously from at least three GPS satellites. This assumes constant good reception of these satellites and is difficult to ensure particularly in densely built-up areas. In the event of defective reception errors occur in the route guidance, particularly in regions in which the direction of motion towards the destination changes at short intervals.
Numerous publications disclose the use of electronic compass sensors for navigation purposes. The company Precision Navigation, Inc., Canada, for example, manufactures such sensors. Instead of rotatably mounted magnetic needle such modules use two inductors oriented at right angles to one another in order using the earth's magnetic field to determine the orientation of a device relative to the points of the compass. In a computation process the orientation can be calculated directly in degrees. Accuracies of less than 5° can be achieved at low cost and with comparatively little effort